A New Genus for Alkaliphilic Strains of Gram-positive, Endospore-forming Rods
Jin TAMAOKA* and Koki HORIKOSHI
The DEEPSTAR group, Japan Marine Science and Technology Center, Natsushima 2-15, Yokosuka 237, Japan
The genus Bacillus is well known for its versatility and many species that are found everywhere, in rivers, soils, seas, and air. Almost all of species of the genus Bacillus have optimum growth at neutral pH, but some strains that tentatively belong to the genus Bacillus grow well in alkaline conditions, at pH 9-10. These alkaliphilic strains shared some characteristics with strains of the genus Bacillus, such as gram- positive, spore-forming, motile with peritrichous flagella, and are facultative anaerobic rod-shaped. However, these alkaliphilic strains showed many characteristics different from those of known Bacillus species. We characterized these alkaliphilic strains by physiological, chemotaxonomical and phylogenetic methods to determine their taxonomic position. Physiological characters and chemotaxonomical characters of alkaliphilic Bacillus strains and of 17 type strains of the genus Bacillus were analyzed and compared. The alkaliphilic strains were grouped into several clusters on the basis of chemotaxonomical data, such as G+C content, cellular fatty acid composition and menaquinone composition. One of the cluster that consists of the strains No. 2b-2 and others has different menaquinone composition from that of the known Bacillus species. Similarities of 16S ribosomal RNA sequences between these alkaliphilic strains and Bacillus subtilis are about 90%. And they are clustered as an independent line of a phylogenetic tree based on the 16S ribosomal RNA sequences. On the basis of these results, we are proposing a new genus for these alkaliphilic strains.
